How to create an alert in a subview class in Swift? - ios

Question

I have a view controller which contains a sub-view. And inside the sub-view class, I may need to pop out an alert when some condition is satisfied.
class GameViewController: UIViewController {
#IBOutlet var gameBoardUIView: GameBoardUIView
...
}
class GameBoardUIView: UIView {
...
func move() {
if !gameBoard.checkNextMoveExist() {
var alert = UIAlertController(title: "Game Over", message: nil, preferredStyle: UIAlertControllerStyle.Alert)
alert.addAction(UIAlertAction(title: "Take Me Back", style: UIAlertActionStyle.Cancel, handler: {(action: UIAlertAction!) in
println("Taking user back to the game without restarting")
}))
alert.addAction(UIAlertAction(title: "New Game", style: UIAlertActionStyle.Destructive, handler: {(action: UIAlertAction!) in
println("Starting a new game")
self.restartGame()
}))
// This is where the question is
// self.presentViewController(alert, animated: true, completion: nil)
}
}
}
As you can see from the code, I cannot call presentViewController function to show the alert because my sub view is not a controller class. Should I somehow create a week reference to the parent controller inside the sub-view? What would be the best practice to implement such reference?

Answer 1

Swift 4
Just present the alert in UIApplication windows in root view controller:
let title = "Some title"
let message = "body message"
let alert = UIAlertController(title: title, message: message, preferredStyle: .alert)
let action = UIAlertAction(title: "Aceptar", style: .cancel, handler: nil)
alert.addAction(action)
UIApplication.shared.keyWindow?.rootViewController?.present(alert, animated: true, completion: nil)

Answer 2

there are couple of ways how you can catch a UIViewController in your UIView.
you can make any of your view controllers as a delegate to show an alert;
you can pass a view controller's reference to your view; and
in general you can always grab the rootViewController anywhere in your code.
you need to call the dismissViewControllerAnimated(_: completion:) on the same view controller when you'd like to dismiss your alert later.
thus, I'd do such a quick solution for your case:
func move() {
if !gameBoard.checkNextMoveExist() {
let rootViewController: UIViewController = UIApplication.sharedApplication().windows[0].rootViewController
var alert = UIAlertController(title: "Game Over", message: nil, preferredStyle: UIAlertControllerStyle.Alert)
alert.addAction(UIAlertAction(title: "Take Me Back", style: UIAlertActionStyle.Cancel, handler: {(action: UIAlertAction!) in
rootViewController.dismissViewControllerAnimated(true, completion: nil)
println("Taking user back to the game without restarting")
}))
alert.addAction(UIAlertAction(title: "New Game", style: UIAlertActionStyle.Destructive, handler: {(action: UIAlertAction!) in
rootViewController.dismissViewControllerAnimated(true, completion: nil)
println("Starting a new game")
self.restartGame()
}))
rootViewController.presentViewController(alert, animated: true, completion: nil)
}
}